Purpose: To elucidate long-term sequelae of radiation therapy (RT) in head and neck cancer (HNC) patients, a multicenter, prospective study, Clinical Registry of Dental Outcomes in Head and Neck Cancer Patients (OraRad), was established with tooth failure as its primary outcome. We report tooth failure and associated risk factors.

Methods and materials: Demographics and cancer and dental disease characteristics were documented in 572 HNC patients at baseline and 6, 12, 18, and 24 months after RT. Eligible patients were aged 18 or older, diagnosed with HNC, and receiving RT to treat HNC. Tooth failure during follow-up was defined as losing a tooth or having a tooth deemed hopeless. Analyses of time to first tooth-failure event and number of teeth that failed used Kaplan-Meier estimators, Cox regression, and generalized linear models.

Results: At 2 years, the estimated fraction of tooth failure was 17.8% (95% confidence interval, 14.3%-21.3%). The number of teeth that failed was higher for those with fewer teeth at baseline (P < .0001), greater reduction in salivary flow rate (P = .013), and noncompliance with daily oral hygiene (P = .03). Patients with dental caries at baseline had a higher risk of tooth failure with decreased salivary flow. Patients who were oral-hygiene noncompliant at baseline but compliant at all follow-up visits had the fewest teeth that failed; greatest tooth failure occurred in participants who were noncompliant at baseline and follow-up.

Conclusions: Despite pre-RT dental management, substantial tooth failure occurs within 2 years after RT for HNC. Identified factors may help to predict or reduce risk of post-RT tooth failure.